Impact of Peri-Operative Hyponatremia on Postoperative Outcomes in Major HPB Surgeries for Cancers

The present study is being designed to study the impact and predictive nature of perioperative hyponatremia on post operative outcomes in patients undergoing Major HPB surgeries for cancers. Major hepatobiliary-pancreatic surgeries will be defined as follows- * Pancreaticoduodenectomy, * Hemihepatectomy or greater with or without caudate lobectomy * Extrahepatic bile duct resection * Extended cholecystectomy * Distal Pancreatectomy with or without splenectomy The primary Objective of the study would be to compare post operative major morbidities and early mortality (\<90 day) in major HPB surgeries done for cancer patients with and without peri-operative hyponatremia. (\<135mmoL/L). Development of systemic complications and long term outcomes (overall survival and disease free survival) will also be evaluated. It will be an observational study consisting of both, a retrospective arm and a prospective arm. All consecutive patients undergoing major HPB surgery from 2010 till 30th June 2024 will be included in the study.